Tab control



Feb. 16, 1954 c. A. BOSSERMAN TAB CONTROL 3 Sheets-Sheet 1 Filed May 17, 1952 JNVENTOR. 04/482594 KOS'SEFMAA BY Wh A G'A/T Feb. 16, 1954 c. A. BOSSERMAN 2,669,401

TAB CONTROL Filed May 17, 1952 3 Sheets-Sheet 2 BY W Feb. 16, 1954 c. A. BOSSERMAN 2,669,401

TAB CONTROL Filed May 17, 1952 3 Sheets-Sheet 3 INVENTOR. 64445256 450555014 C QM QM Patented Feb. 16, 1954 zififi M e ABT 591 enemies A Bosserman, Seattle. Wa h it e s n Common... Seattle. west; e lgware This: invention relates to improvementsa in. control means; fon-r udd'ersand other-controls feoesmnd the tabs-thereon; andg more portion: larly,:-concerns.e control: system. employin a tab.

which alternatively serves as; a. direct action.

qreete a o he: am ta in: such; dir on ha the oo; l, ssistther urnine; o e sur ace upo eilu of th pow o st. B ei mb n. he em 2: Q- a l-I r .18.E at a newer: te ur au om ticall permits the actuat on of. a r n oa e mach: enism hene nee ran ermn tiq h inleage, thereby e e ing: h ota on o t b, caused v e n ot r etedr mo ion n; iv n sense...

The m gnitude o con o urf cee and! power boost acc o req i edt op rate. them hemmade t eas elv d-ifl lt toobtein p ec s n; p r t on. w en s a l; cor ective. WONG? merits of he. c ntrols u aces dcired;-.

The e rpo of is. mot n; iso retentive: ood; flv ne erec e ice whe co -1 motio s are: desired 1v m lot' eet serve.

11 Q1; ur e et t m. o crrectionn e e l hetcthere "deed: s ot-*- Q the hydraulic boos m. encounter d; control mechani m or he. tab; su em nt:- ing the powered conventional. controls. of the 40 surfacesn; occompl ehrine; th ei purpos it is; an object. 1?; 13h invention to automatically convert the z ll Q i qnz Ofthe tab; from odireot. acting control. surface under normal operating: conditione to an, eseistingservo, tab surface upon failure of the. power boost system. The conversion occurs. upon the; loss, of: hydraulic. pressure permitting a; spring forceto alter the position of a portion. of the 6. 9 control linkages so. the tab. operates the. reverse sense to move the. control surface into. another position assisting the. pilot in his. manual" movement of' the surface by: the controls preyioi sly poweropemted;

. The purpose and. object at the: invention will hee teqy 2:. become more epparent asthe following descrip:. tion; is-greadainloonjunction with ther accompanying-drawings wherein-i thev same parts, are notedi, throughout the: severelr views by. like numerals In. theedraiwingsa Figure. 1: is, a, sohematie perspective. sectional; viewishowing the assembly; when thepower-boost system: is: energized:

Eigni'e 2 is a. view similar-toiFigurel showing. theiassembly when; thepower boost-system. is not energized;

Figureiii isa schematic viewsimi'lal to Figure 25 indicating? the related motions. of? some of the. movable.componentswhen: the power, boost sys.-..

tern,v isnin. operation;

Figure Us a. schematicview. similar torFigur-er 2-. indicating the related-gmotions: of someofthe movable; components,vvhenv the power boost sys-. tern heslfailed.

lt ioreipamticularly, the invention asiapplied to. rudder controls comprises a. tab Ill hinged: on. a. rudder; l1'l of. an airplane fin [2s and: controlled. byenassembl-y of; components.- responsive to the. initial movement oi -a1. torqueitube. I .3. in theifin I12 4 as: it: is: aetuateda by the. pilot through controls (not, shown); The rotation of. the: tube. 113 is transmitted: through. its armto. a tab control rode I15; extending. from the for [2" into the rudden l st, where. itis connecterlv to. a, tab control cross arm'. iliirotatably mounted Within the. rudden I I.: one pin H". 6n the opposite. end of'thecross: arm l6. is; a. deflected. extending: yoke 18 pivotal-ly supportinge belli era-nit It on a pin. 2.0: perpendicular to and: below. the pin t1;

Another tab control rool 2l is ettached to the o 4% 0 he e s nk; and n s.- he. midpoint Hot a multiplier lever; 24 to rotate it; about a pivotal; axis 2 5 secured; to the rudder permittingmotion of the lever 24 in a plane p re li i o t e in e o th water- 'Ijhe thirdtab control; rorl 2 51s seol reg'to the 1 the ve :4. we. ne de. the ee ilwhere it s en d: f qe e z he. h n il; en at tr nem ie when hieb. rotates th tap ti} th resultin ta l t ee. eon. EYQEWQ with. P Q J. K th iqttiqll f. .6 9 3 W 3.. I-3* and gross arm It; by altering the position oi e be i ronla 1 ,.eq. th e. .2.: is he npeeite side; of the ra n. The b l ra it ut t ally moved. y a. prite ee. s1. w ll: nte 9. u t h er sse rm. .5 2.1 the e: tre t nrt e spr bia e .ne 7q a when t t q ier creeken at hen. he

powenboost is no longer energized.

A hydraulic powered boost system is shown by way of example to illustrate how the tab control linkage is combined with conventional rudder controls to obtain the desired purpose of the invention. Oil under pressure is carried by line 32 through an electrically powered shut-off valve 33 and a valve actuator 34 to a Y portion 35, one fork 36 leading to a pressure regulator 31 and then on to the actuator 29, moving the piston end of the plunger-rod 39 by hydraulic pressure against the action of a spring within the actuator 29.

The other fork 38 of the Y portion 35 directs oil under pressure into valve 39 where distribution of the oil is made to a hydraulic cylinder 48 mounted in the fin 12, through lines 41 and 42, interconnected by a by-pass 43 and valve 44. The piston and rod 45 actuated by the oil in the cylinder control the movement of the rudder II. The piston rod 45 is attached to the rudder H at one side by a pin 55 near the rudder hinge line.

The valve 39 is actuated by motion of a connecting link 41 which is moved by the rotation of a cross header 48 pivotally mounted above the arm l4 on a shaft 43 between the midpoints of the arm it and the cross header 48, respectively. The end 59 of the cross header 68 is connected to the rudder by link preventing its movement until the rudder moves. As a result, when the arm [4 rotates the cross header t8 counter-rotate relative to the arm It commencing "the motion of the connecting valve link 4'! which increases as the arm It continues to swing. The valve 39 then directs the flow of hydraulic fluid to the cylinder Ml so the action of the piston rod 45 will effectively rotate the rudder II.

During the preliminary motion of the arm [4 when the cross header .8 does not change its position su'mciently to open valve 39, the tab control linkage operates quickly to turn the tab. Subsequently as more rudder action is desired the power boost system will be effective upon the continued rotation of the torque tube. In this way the inventive linkage serves the first purpose under normal operating conditions to move the tab to supply an immediate aerodynamic action equivalent to that of a small rudder.

Failure of the supply of hydraulic pressure for the power boost system is immediately detected by the hydraulic spring loaded actuator 29, the spring motion becoming effective to alter the position of the bell crank l9 arranging the linkages to move the tab in in the reverse sense for assisting the pilot in manually turning the rudder.

Figures 3 and 4 depict the end result of both these purposes of the control system. In Figure 3 the inventive linkage is shown rotating the tab as a small rudder in the same direction as the anticipated movement of the rudder under power operation. In Figure 4, the tab is controlled by the rearranged linkage to serve as an aerodynamic servo tab assisting the pilot as he turns the rudder when the power boost is off.

Other features include: stops 52, 53 mounted on the rudder H to define the operational limits of the tab control cross arm I6 relative to the rudder ll so that continued attempts to move the cross arm l8 result in direct manual movement of the rudder; an automatic control device comprising the valve actuator 34 which senses the hydraulic failure and by a mechanical means 55 actuates the valve 44 in the by-pass line 43 avoiding a hydraulic locking effect which might prevent manual operation of; the control system;

4 l the hydraulic discharge 54; and a. pressure regulator 31 used to variably oppose the spring action of the actuator 29 as a means of varying the radial location of the bell crank end 22 from the pin 11 which is located approximately on the centerline of the rudder H, thereby permitting control of the sensitivity of the tab when it operates as a small rudder; for example, when the hydraulic pressure completely opposes the spring action, the end 22 is turned on its maximum radius rotating the tab to a greater angle for a given rotation of the arm M as effected by the pilot.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed I declare that what I claim is: V

1. In an airplane control system employing a power boost system and tabs on larger airfoils, a means for operating the tabs alternately as a small airfoil when the power boost is energized and as a servo tab when the power boost is not energized, comprising a cross arm rotatably mountable at one end within a large airfoil; a pilot actuated control rod connected to the other end of the cross arm; a deflected extending yoke integral with the cross arm and terminating below its mounted end; a bell crank pivotally fastened to the yoke; a second control rod connected to one end of the bell crank and attachable to tab linkages; and a bell crank actuator mounted on the central portion of the cross arm and connected to the other end of the bell crank, the actuator containing a spring normally compressed by the force of the power boost system but expandable upon a power failure to actuate the bell crank, thereby changing the rotational direction of the effective force transmitted to the second control rod as the pilot actuated control rod operates in the same direction. t

2. In an airfoil control apparatus, the combination of: a power boost system; a movably supported main airfoil; an auxiliary airfoil mounted on the main airfoil for control movement independent thereof; an auxiliary airfoil control member mounted in the main airfoil consisting of a cross arm pivoted at one end; a bell crank attached to the cross arm below its pivot; a bell crank spring actuator mounted on the cross arm and interconnected between one arm of the bell crank and the power boost system; control rods and linkages connected to the movable end of the cross arm to transmit to it pilot created forces; and control rods and linkages connected to the other end of the bell crank to transmit its motion to the auxiliary airfoil, the resulting direction of rotation of the auxiliary airfoil being dependent on the position of the bell crank which moves under spring force when the power boost system is de-energized.

3. A tab control mechanism for incorporation into an airplane control system utilizing a power boost for operating the main control surfaces comprising a cross arm pivotally mountable at one end within a main control surface, a bell crank attached to the cross arm below its mounted end, a bell crank spring actuator mounted on the cross arm and connected to one end of the bell crank and attachable to a power boost system, control rods and linkages connected to the movable end of the cross arm and extendable for attachment to pilot controls for transmission of the pilot created forces to the tab control mechanism, and another set of control.

rods and linkages connected to the other end of spring of the actuator becomes effective upon the shut down of the power boost.

4. In an airplane airfoil control system a tab control directly interconnected with a power boost system, comprising a cross arm for pivotal mounting in an airfoil With its free end subject to pilot manipulation, a bell crank mounted below the pivotal axis of the cross arm and connected thereto, and a spring actuator mounted on the cross arm and connected to one arm of the bell crank and made responsive to existence of power in the boost system, the other arm of the bell crank attachable to tab linkages, whereby movement of the bell crank caused by the actuator upon failure of the boost system changes the location of the other arm of the bell crank with respect to the pivotal axis of the cross arm thereby changing the direction of rotation of the tab although the pilot manipulation continues in the same sense.

CHARLES A. BOSSERMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,395,671 Kleinhans et a1. Feb 26, 1946 2,585,411 Schultz et a1. Feb. 12, 1952 

